The enzymic preparation of fats that can be used as human milk fat replacers, in which fats more than 40 wt. % of the total amount of saturated fatty acids present are in the 2-position, is the subject of our earlier European patent 0209327 (Application N.degree. 86305325.2) and European patent application 91300496.6.
According to these processes, fats (A) high in trisaturated triglycerides (=S.sub.3, wherein S is preferably palmitic) are converted with a source (B) that provides oleic acid moieties. Sources of B are, e.g., free fatty acid mixtures rich in oleic acid or triglycerides with a high oleic acid content in the 1,3-positions, e.g. high-oleic sunflower oil.
The conversion is carried out in the presence of a 1,3-specific enzyme. The product of this enzymic conversion containing residual amounts of non-converted S.sub.3, partial conversion products, such as SSO, and the desired conversion products (OSO), is subjected to a fractionation process in which a product rich in OSO is obtained while a product rich in SSO is removed and recirculated to the conversion zone. Spent oleic acid sources (B) are removed in a strip zone and can be used again in the process, if and when appropriate.
Human milk replacement fats can only contain very limited amounts of trisaturated triglycerides (S.sub.3, where S=saturated fatty acid with at least 16 C-atoms). When the amount of S.sub.3 is too high, the fat becomes too hard, and simultaneously absorption of the fat by infants is affected adversely.
However, the products obtained in the enzymic conversion zone normally still contain amounts of 7 or more wt. % of S.sub.3, which is above the level, generally regarded as acceptable (about 4 wt %). Only when these products were subjected to solvent fractionation could these levels be decreased to the desired level. However, wet fractionation requires high investments in equipment, time and energy and is therefore less attractive from a commercial point of view.